This invention relates generally to apparatus and methods for transporting, storing and dispensing very viscous semisolid products, and more particularly to an ASME pressure vessel having a pig delivery system whereby pressurized gas, greater than 15 psig, is used to effectively extrude viscous material out of the apparatus.
As used herein, the term xe2x80x9ctankxe2x80x9d is used define a container limited to internal pressures of less than 15 psig, and the term xe2x80x9cvesselxe2x80x9d is used define a container capable of withstanding internal pressures of a magnitude greater than 15 psig. The prior art generally teaches xe2x80x9ctanksxe2x80x9d, that are limited to internal pressures of less than 15 psig, and consequently, limited to dispensing products of low viscosity.
Bulk transport and dispensing of viscous semisolid products has commonly been accomplished in non-metallic and metallic containers capable of being pressurized with gas and having a piston follower which moves in response to the gas pressure applied to the top of the piston follower and thereby transferring force over a wide cross-sectional area to the viscous semisolid product below the piston follower and causing the semisolid product to flow from the container.
The prior art can be divided into two categories. The first category generally comprises small pressurized apparatus and dispensing methods utilized in non-bulk delivery and dispensing of small volumes of product like toothpaste and shaving cream. The second category of prior art generally comprises larger equipment designed to transport and dispense bulk volumes of semisolid products like grease or non-viscous products that must be isolated from the atmosphere. The terminology most often used to denote bulk liquid transportation equipment is xe2x80x9ctotexe2x80x9d or more precisely, an Intermediate Bulk Container or xe2x80x9cIBCxe2x80x9d.
Typically, an Intermediate Bulk Container or xe2x80x9cIBCxe2x80x9d is simply a container ranging in size from 85 gallons to 550 gallons and come in a variety of shapes and are fabricated using a variety of materials, such as plastic, aluminum, steel and stainless steel. They are typically used for shipping bulk liquids and not intended to be capable of withstanding the application of internal pressure. The prior art dealing with the particular category of bulk transport and dispensing tanks specifically designed to be capable of withstanding internal pressures is typically limited to dispensing gas pressures having a magnitude of less than 15 psig.
In contrast, the apparatus and methods of the present invention are designed for the specific purpose of transporting, storing and dispensing highly viscous materials that require dispensing gas pressures of 15 psig and greater.
The low-pressure limitation of the prior art defines the difference between a xe2x80x9ctankxe2x80x9d or xe2x80x9cIBCxe2x80x9d of the prior art, and an ASME xe2x80x9cpressure vesselxe2x80x9d in accordance with the present invention. As discussed hereinafter below, prior art xe2x80x9ctanksxe2x80x9d and xe2x80x9cIBC""sxe2x80x9d are designed and engineered to meet federal standards that are different from the federal standards that are met by the xe2x80x9cASME vesselsxe2x80x9d of the present invention, and is an important distinction and difference between the prior art and the present invention.
There are several patents that teach Intermediate Bulk Containers (xe2x80x9cIBC""sxe2x80x9d) and xe2x80x9ctanksxe2x80x9d for transport or storage and dispensing of semisolid and fluid materials, such as grease and oil, which utilize piston members with various specially designed seals that dispense the contents. Some of these patents recite inflation pressures for inflating the seals, but are silent as to the viscosities of the materials and the internal design pressure of the tank and the dispensing pressures. Since the containers are referred to as a xe2x80x9ctankxe2x80x9d and the tank diameters taught in the patents are large, it is assumed by reference to the ASME Boiler and Pressure Vessel Code, Section VIII, Division 1, for the design of pressure containing vessels, that the limiting design pressure is less than and/or substantially less than 15 psig, and consequently, that they are limited to dispensing products of low viscosity
Watson, U.S. Pat. Nos. 4,721,235, 5,114,054, and 5,341,726, disclose an elongate generally cylindrical tank for transport or for storage in bulk of semisolid and fluid materials, such as grease and oil. The tank has cylindrical piston that carries a hollow inflatable seal in a circumferential channel around the piston. A pressurizing device varies the pressure within the seal between atmospheric pressure and a pressure higher than atmospheric wherein the seal expands and presses against the internal surface of the tank.
Watson, U.S. Pat. No. 5,746,112 discloses an elongate generally cylindrical tank for transport or for storage in bulk of semisolid and fluid materials, such as grease and oil. The tank has cylindrical piston and a piston member that carries an annular elastic seal. The seal has an annular crown projecting radially outwardly from the piston member and engageable with the interior surface of the tank. The seal has a pair of spaced apart legs supporting the crown, and an arrangement for squeezing the legs together to move the crown outwardly and cause it to be pressed against the interior surface of the tank with a pressure such that when the piston member slides in the tank a portion of the crown is maintained in sliding engagement with the interior surface thereby to wipe the material therefrom and to seal the piston member relative to the tank.
Popp et al, U.S. Pat, No. 5,887,750 discloses an intermediate bulk container (xe2x80x9cIBCxe2x80x9d or xe2x80x9ctankxe2x80x9d) that is open substantially the full diameter at the top with an outwardly extending flange and an inner sealing band extending to a height above the top of the flange. A removable lid sitting on the body has a cylindrical side wall depending down and terminating with an outwardly extending lid flange forming an obtuse angle with the side wall, wherein the lid is adapted to sit on the open end of the body with the lid flange above the body flange and the sealing band overlapping the lid side wall. A channel is formed between the inner sealing band, the body flange and the lid flange. A gasket is placed in the channel and the gasket is compressed between the body flange and the lid flange for sealing the container. The large opening facilitates cryogenic cleaning of commodity residue from the interior. The system includes a rotating base to turn the container to facilitate freezing and removal of the residue.
Berry, Sr., et al, U.S. Pat. Nos. 6,027,123 and 6,325,384 disclose tank pistons with an improved seal and wiper that are used in conjunction with tanks for transporting semi-solid and viscous materials such as grease, oil, ink, and the like. The improved seals consist of an annular rubber member with a hollow chamber filled with an open cell foam material such as polyurethane, or a gel such as silica gel. The material in the chamber is compressible and expandable to provide a seal about the piston. The pistons may also be provided with an annular wiper structure that extends about the outer forward periphery of the piston, and is forwardly angled at about 45 degrees relative to an axis of the piston. The wiper has a beveled end that makes contact with the interior surface of the tank to provide a cleaning action. A complementary second wiper may be added near the outer rearward periphery of the piston.
Popp et al, U.S. Pat. No. 6,206,248 discloses a piston for dispensing material from a tank that includes a nose section connected to a piston shaft. A recessed channel is located between the nose section and piston shaft. In the channel, there is a seal lifter over which a solid wiping seal is placed. Upon inflation, the seal lifter forces the wiping seal to extend beyond the periphery of the piston to come into sealing contact with the interior wall of the container.
U.S. Code of Federal Regulations 49 CFR Paragraph 178.705, incorporated herein by reference, lists the standards for metal Intermediate Bulk Containers or xe2x80x9cIBC""S, such as those of the prior art. Paragraph 178.705 of 49 CFR discusses the required material properties and minimum wall thickness needed for the safe containment and transportation of hazardous materials in IBC""s. 49 CFR178.705 subtopic iv paragraph C, subpart ii, states a requirement for hazardous material IBC""s citing the start-to-discharge pressure of a pressure relief device fitted on an IBC may not be higher than 9 psig. Clearly, IBC""s designed to satisfy the requirements of 49 CFR178.705 would not be suitable for the transport and dispensing of highly viscous materials requiring pressures of 15 psig and greater to displace the material from the IBC.
The present invention far exceeds the requirements for classification as an IBC. The vessels of the present invention have an internal operating pressure exceeding 15 psig, and are designed for the specific purpose of transporting, storing and dispensing viscous materials that will not dispense at pressures below 15 psig and require dispensing gas pressures of 15 psig and greater.
The pressure vessels of the present invention are constructed in accordance with ASME Boiler and Pressure Vessel Code, Section VIII, Division 1, incorporated herein by reference. U.S. Code of Federal Regulations 46 CFR Ch. 1, Paragraph 54.01-2 incorporates by reference, the ASME Boiler and Pressure Vessel Code, Section VIII, Division 1. Paragraphs U-1c(2)(h) and U-1c(2)(j) of Section VIII, Division 1, of the 2001 ASME Boiler and Pressure Vessel Code define the scope of application to the pressure design of vessels having an internal operating pressure greater than 103 kPa (15 psig) and less than 20685 kPA (3000 psig). Thus, although the pressure vessels in accordance with the present invention are used for transporting materials in a manner somewhat similar to an IBC, the normative reference and mandatory design requirements are dictated by those used for pressure vessels and not IBC""s since the operating pressure is greater than 15 psig.
Pipeline pigs are commonly used in oifield and refinery operations. The conventional pipeline pig comprises a generally cylindrical plug that moves through the inside of a pipeline for the purpose of cleaning, dimensioning, inspecting, or to separate dissimilar fluids. Typically, the pigs have a metal (steel or aluminum) body or steel shaft and are equipped with annular flexible seals (scraper cups or discs) that seal on the interior diameter of the pipeline to allow the build-up of differential pressure required to propel the pig through the pipeline. These pigs are unidirectional if they have scraper cups and bidirectional if equipped with discs. Typically, pigs are launched into the pipeline through a pig launcher connected to the pipeline, and are received in a pig receiver or trap connected to the pipeline after they have made a successful run through the pipeline.
Pipeline pigs have not heretofore been employed in pressure vessels for the purpose of effectively extruding very viscous semisolid materials from the pressure vessel apparatus.
The present invention provides a method for the transportation and point-of-use dispensing of very viscous, semisolid products where the viscosity of the semisolid requires that the apparatus of the invention include the use of a pressure vessel(s) capable of withstanding internal pressure greater than 15 psig. With the method and the apparatus of the invention, semisolids having large viscosities may be safely transported, stored and dispensed.
The apparatus of the present invention generally comprises one or more pressure vessels, flanged on at least one end and mounted either vertically or horizontally on a skid base, with each vessel containing a bi-directional pipeline pig, which acts as a piston, whereby gas pressure may be introduced on one side of the pig, forcing the pig to move through the vessel until it stops at the end of the vessel, thereby displacing product material contained between the pig and the end of the vessel through an outlet located at the end of the vessel. The vessel(s) is outfitted with a pressure/vacuum relief device, an outlet isolation full port valve of a sufficient diameter for the dispensing of very viscous semisolid product, a gas connection and isolation valve for the introduction of pressurized gas, a vent valve for the evacuation of pressurized gas to atmosphere, a magnetically operated indicator or such other means for detecting the location of the pig inside the vessel. The skid comprises a base for securely attaching the vessel(s), with channel openings in the base to allow the skid to be picked up with a fork truck, and with lifting eyes included either on the skid or on the vessel(s) allowing the entire skid to be picked up with slings and shackles using an overhead crane.
The method of the invention allows filling of the apparatus with very viscous semisolid product, using a pump or such other method, making sure that the vent valve above the pig is open to allow displaced air or gas to escape, and whereby the vessel(s) is completely filled and the pig is displaced by product to the fullest extent of travel inside the vessel(s). The skid may be picked up, moved about and transported to the point of use. Dispensing is accomplished by positioning the skid in the appropriate location, supplying air or gas pressure at 15 to 125 psig pressure to the vessel connection, making sure the vent valve is closed, open the product valve, and slowly open the gas supply valve introducing pressure above the pig, causing it to move, thereby displacing product out of the vessel and product valve.